Means and methods for color sorting articles



`lune 13, 1961 H. w. BARTLETT MEANS AND METHODS FOR COLOR SORTING ARTICLES Filed March 23, 1953 4 Sheets-Sheet l June 13, 1961 H. w. BARTLETT 2,983,219

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June 13, 1961 H. w. BARTLETT MEANS AND METHODS FOR COLOR SORTING ARTICLES 4 Sheets-Sheet 4 Filed March 25, 1953 INVENTOR. /Q/Po W @f7/P72577 /7TT0/ENEVS Unite States Patent O "f' 2,933,219 MEANS AND METHODS FR "COLOR SRTlNG ARTICLES Harold W. Bartlett, Berkeley, Calif., assigner to California Packing Corporation, 'San Francisco, Calif., a

corporation of New York Filed Mar. 23, 1953, Ser. No. 344,103 3l Claims. (Cl. 209-111) The present invention relates to means and techniques useful in sorting or grading articles such as, for example, comestibles, in accordance with the shade or color of such articles and has particular applicability in an arrangement for automatically and continuously sorting or grading food products or comestibles such as peaches, although the invention, of course, is not limited to such use but is applicable also to the sorting, grading, or classification of all colored objects and food products, such as vegetables' and fruits, both fresh and dried, which vary in color as they mature or ripen.

The present application constitutes a continuation-inpart of my co-pending patent application Serial No. 80,865, filed March ll, 1949, and assigned to the present assignee, now abandoned.

'I'he present invention involves the use of a diffused light source, since applicant has found that, in order to successfully sort peach halves in accordance with small color shade differentials, light reflected by the peach to the phototubes should first be diffused before impinging on the peach.

Some means in the form of a voltage regulator is provided to eliminate the highly undesirable results which are occasioned by variations of the voltage applied to the applicants light source.

A filament type white light source is used because all colors to be reflected for proper classication are present. Accordingly, since white light contains all of the color components in the visible spectrum, objects of any color may be sorted by merely changing the relative color sensitivity of the present arrangement which includes a par of photocells, each responsive to different spectral distributions of light in the visible spectrum.

Applicants arrangement of photocells in conjunction with the amplifying or electrometer tube is extremely sensitive and serves to make determinations of color differences that cannot be distinguished by the eye. In order to obtain such determinations, it has been found desirable to use only the light reflected from a single unitary spot on the peach half and to split such light into two beams, one beam being directed to -a so-called green photocell and the other beam being directed to a so-called red photocell.

The arrangement shown herein uses a pair of photocells, each being sensitive to different spectral distribution of energy reflected from a comestible, i.e., peach half, being so due t either the use of different color responsive photocellsl or to the use of different color filters, with the light reflected on each of the photocells being derived from the same single unitary spot on the comestible. Further, only one spot is viewed at a particular time, such spot being substantially less than the projected area of the peach half so that, effectively, the peach half is scanned in its movement past the phototubes. It is apparent, of course, applicants invention is applicable to sort articles on the basis of `a classification made by viewing either substantially the entire object progressively, i.e., scanning, or a small part thereof at one time by taking a snapshot of said article at the instant it reaches a predetermined point of selection as more fully set forth hereinafter. But such classification obtained by snapshot methods is not considered as desirable as that derived through progressive scanning of the entire article for 2,938,219 Patented June 13, 1961 ICC the reason that, using snapshot methods, small green areas which might make the entire comestible unsatisfactory from the practical standpoint either would be classified according to an average or would be entirely ignored, which in effect, amounts to overlooking them entirely.

It is, therefore, an object of the present invention to provide a commercially practical arrangement for sorting comestibles according to their degree of ripeness, the arrangement being characterized by the fact that it depends for its .operation on the color or shade of light reflected from the comestible.

Another object of the present invention is to provide an improved arrangement employing photoelectric cells which are connected and energized in a novel manner to achieve a practical color sorting arrangement.

Another object of the present invention is to provide an improved sorting arrangement responsive to color, characterized by the fact that a plurality of photoelectric cells, each inherently more sensitive to different colors, or rendered so by the use of color fiilters, are arranged in a novel manner, a subsidiary feature being that means including additional photocells are provided whereby compensation is accomplished for variations which otherwise would occur due to change in spectral distribution of light from the source illuminating such plurality of cells.

A further object of the present invention is to provide an improved circuit incorporating a pair of photoelectric cells, each of which is either inherently sensitive to a different color or rendered so by the use of colored lters, one of the important features of the circuit being its sensitivity.

Yet another object of the present invention is to provide an improved color sorting arrangement in which articles to be sorted are moved past a scanning head to derive therefrom intelligence as to their degree of ripeness, such arrangement having associated therewith a time delay mechanism, or memory apparatus, whereby such intelligence is used to deflect such article after it passes an appreciable distance beyond the scanning head.

Still a further object of the present invention is to provide an improved color sorting arrangement characterized by the fact that the results obtained are in accordance with color shades or reflections in the visible spectrum and are substantially unaffected by radiation occurring outside the visible spectrum, such as that due to reflectance of the chlorophyll content of the comestible.

Still another object of the present invention is to provide an improved color sorting arrangement for sorting articles with chlorophyll content depending for its operation on the use of light reflected from such articles.

Still another important object of the present invention is to provide an arrangement of this character which depends for its operation on the use of diffused light so that highlights from the comestible are eliminated and satisfactory readings obtained.

Still `a further object of the present invention is to provide an arrangement of this character which not only uses diffused light but which has associated therewith means for maintaining the voltage applied to the illuminating lsource of constant intensities so that changes in the spectral distribution of the light produced by such source has no appreciable effect on the determinations.

A further object of the present invention is to provide improved means and techniques whereby the effect of reflectance of the chlorophyll of a comestible may be practically eliminated or substantially reduced to allow such comestibles to be accurately classified in accordance with many degrees of ripeness.

Still another object of the present invention is to provide improved means whereby the photocell means is arranged to receive reected light progressively from diiferent fractional portions of said objects so as to, in effect, obtain a scanning action.

Yet another object of the present invention is to provide an improved arrangement of this character which embodies the concept of viewing only a fractional part of the peach half, i.e., in the order of 15 percent of the same, while the peach half moves, to effect a scanning action during which a multiplicity of measurements (which may be considered to be an innite number of measurements) may be produced with sorting of the peach half accomplished, however, in accordance with only one of such measurements, with the result that the peach may be classified according to the greenest (or ripest) part scanned.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 shows apparatus incorporating features of the present invention, such apparatus being shown partially in schematic and partially in stnuctural form.

FIGURE 2 illustrates the manner in which the viewing angle changes when and as a peach half moves under the scanning head.

FIGURE 3 is a sectional view taken substantially on the line 3-3 of FIGURE 2.

FIGURE 4 illustrates the manner in which a different but single -unitary spot on a peach half is successively and continuously viewed in its motion past the generally elliptical aperture illustrated in FIGURE 2 to achieve a scanning action.

FIGURE 5 illustrates a longitudinal sectional view through a connnercial version of the scanning head illustrated in FIGURES 1 and 2.

FIGURE 6 is a view in end elevation taken generally in the direction indicated by the lines 6 6 in FIGURE 5 with a portion of the light reflecting dome and tunnel fragmented to show a portion of the internal arrangement.

FIGURE 7 is a view in elevation of the front end of the viewing tube taken generally in the direction indicated by the line 7-7 in FIGURE 6.

`FIGURE 8 illustrates the response of the tubes 20, 21 to the same intensity of light color with the abscissae plotted in terms of angstrom units (A.U.), or millimicrons, i.e., the wave length of the light, and the ordinates are plotted in terms of percentage of resistance change, it being noted that the greatest change corresponding to 100% occurs between 3000 and 7000 angstrom units and that there is substantially no resistance change when the wave length of the light exceeds 700 millimicrons.

FIGURE 9 illustrates a modification of the circuit shown in FIGURE 1 allowing a measurement to be made as to color of an article in accordance with only a socalled snapshot of the article without the necessity of a scanning action for producing operation of tubes 26, 27, 28, 29 and other circuitry which is connected to such tubes in the manner illustrated in FIGURE 1.

IFIGURE 10 illustrates the manner in which the reectance changes with wave length of light for green ripe and medium ripe peach halves.

General description of apparatus The article, comestible or fruit, shown in the form of halved peaches P, each of which has a generally circular cross section, is -fed onto the travelling endless pair of belts 10 and passes under the scanning head 11 which incorporates a light source which comprises the lamp bulbs 40 and photoelectric cells 20 and 21. In general, the scanning head 11 incorporates and provides a means for assassin` illuminating the moving comestible P to derive certain information or measurements with respect to the same. After passing under the scanning head 11, the comestibles are disposed in the receptacle 12 in the event that the fruit is completely ripened. In the event that the fruit is not completely ripened, it is removed from the traveling belt 10 into the receptacles 12A, 12B, 12C, 12D, by the corresponding ejecting mechanism 13, 14, 15, 1o depending upon the degree of ripeness as determined by measurements accomplished using the phototubes 20 and 2.1.

The specific means whereby the ejecting mechanisms 13, 14, 15, 16 are actuated, are described hereinafter under the heading Ejecting Mechanism Operated in Accordance with Measurements Made at Scanning Head. However, in general, intelligence, or measurements, obtained in the scanning head using phototubes 20 and 21 is conveyed to such mechanism 13, 14, 15, 16, as the case may be, in the form of voltages to operate them. Such intelligence, in the form of voltages, is obtained in a novel manner characterizing one of the features of the present invention.

Apparatus for delivering measurements of color shade The scanning head 11 incorporates means for illuminating peach halves traveling under such scanning head, such illuminating comprising a plurality of lamp bulbs 40 mounted on and extending within the circular or hemispherical shaped dome reflector portion 23, In accordance with one feature of the present invention, the light produced by such lamps 40 is diifused. The lamp bulbs are six in number, equally spaced circumferentially on the inner circular portion of the dome, as illust-rated in FIGURE 5. These lamps 40 are conventional six-volt bulbs used, for example, as parking lights of automobiles, but operated at a nominal voltage of 5 volts, such voltage, however, being regulated within close limits by means described hereinafter.

The light produced by each of such six lamps 40 is diffused so that the traveling peach halves P, while under the scanning head 11 and being viewed, are illuminated solely with diffused light. Such light diffusion is accomplished by rendering the most inward portions of the glass bulbs of such lamp bulbs opaque to the transmission of light that might shine directly on the peach in its scanning position and by painting the inner surface of the dome 23 with a thin layer 23A of light-diffusing paint. The lamp bulbs may be so prepared, for example, and as shown in the drawings, by painting such most inward portions of the glass bulbs with a spot 40A of white or aluminum paint so that a layer of light-opaque paint is disposed between the lamp filament and a peach half located centrally within ythe scanning head while it is being Viewed. Thus, the only light which impinges on a peach half, while it is centrally located, is that which is produced by the lamps `and which is reflected from the inner substantially spherical light-diffusing wall of the domelike portion 23. Such light-diffusing layer 23A of paint serves as a means whereby the peach half is illuminated with diffused light. It is observed that the dome-like portion 23 is of sufficiently large dimensions that it also serves as a light shield, shielding a peach half, while it is located centrally, from light emanating from extraneous sources. To `additionally assure such shielding action, the dome-like portion has integrally formed therewith the two semi-cylindrical tunnel portions 23B and 23C, FIG- URE 5, which are essentially tunnels or light shields through which a peach half enters and leaves the scanning head, respectively.

Thus, a peach half, while traveling through the central portion of the scanning head 11 and being viewed by the photocells 20 and 21, is illuminated with diffused light only so that substantially all of the characteristic colors of the light from such lamps are absorbed by the peach half without highlights and with the light reected from gesamt;

such peach half being truly representative of the color shade of the peach half and not necessarily its brightness.

The light thus reflected from the peach half P is viewed in a manner considered novel, as described hereinafter, and is likewise used in a novel manner.

In general, the light reected from a peach hall P, while centrally located in the scanning head, is viewed by an optical system which includes the following elements, namely, the viewing tube 41 having a generally elliptically shaped cross section, as shown in FIGURES 3 and 7; a condensing lens 42; and a half-silvered p-rism 43 which is arranged to transmit on the one hand substantially onehalf of the light through a green lter 44 onto the green phototube 21, and on the other hand to transmit substantially one-half of the reflected light through the red filter 45 onto the red phototube 20. The phototubes 2i), 21 may be of the RCA-931A type, i.e., be substantially identical, or the green `and red filters may be eliminated and a red-sensitive `tube be substituted for tube 20 land a green-sensitive tube be substituted for the tube 21. Either of the two alternate arrangements is deemed to constitute means which is sensitive to different spectral distributions of light reflected from the peach half. Moreover, with only minor changes, any of a number of standard type phototubes could be used in place of the RCA-931A.

It should be carefully observed that the elliptically cross sectioned tube 41 is so shaped and disposed in relationship to a peach half that only about l5 percent of the projected area of a peach half is viewed at any one particular time, the projected area of a peach half being, of course, a circle having the diameter of the original peach. Furthermore, the light impinging on the photocells 20 and 21 at any one particular time is derived from a single unitary spot on the peach half, such spot however continuously changing as the peach half moves to effect a scanning action. Thus, due to relative movement of the peach half with respect to the viewing tube, substantially the entire surface of the peach half is scanned in its transit through and under the scanning head, as indicated in `FIGURE 4.

But while the elliptically cross sectioned tube 41 and progressive viewing have been found to be the most accurate and practical adaptation of my invention for the sorting of peach halves, it should be understood that neither is necessarily indispensable to the accurate sorting of other articles having different physical characteristics. For example, in sorting articles having a substantially uniform color, or where it is not particularly desirable to classify according to the greenest or ripest reading, my invention could be adapted as hereinafter set forth (FIGURE 9) to view all or a relatively small portion of the object without regard to the shape of the viewing aperture and without regard to progressive viewing so `as to take a snapshot of the article as it passes and to classify according to the reading obtained from such snapshot The lower end of the viewing tube 41 is disposed above the peach half a distance of approximately one inch and has its open ended wall of curvature substantially the same as that of the projected area of the peach half. It is observed that the so-called major axis of the elliptically shaped aperture is substantially equal to the diameter of the peach half, i.e., such major axis has a length substantially equal to the dimension of the peach half as measured perpendicular to its direction of movement so that the peach half is scanned as a result of its movement. Thus, substantially the entire peach half is scanned as the peach half completes its passage under the aperture, but only approximately l5 percent of the projected area is viewed at any particular instant. In such passage, the photoelectric cell means continuously derives what may be considered to be an ininite number of measurements which I call progressive viewing; and selection, grading or classification of a peach half, however, is made in accordance with only one of such measurements, i.e., that measurement which indicates the most green condition of `the peach, as described more fully below. In general, if there is a green spot on the peach half, with the remainder of the peach indicating a ripe condition, then the peach half is classied more nearly as a green peach than would be the case if the entire peach half were viewed at the same time. It should be noted that, with only minor adjustments, the present arrangement may be made to classify according to the ripest reading, or according to the reading obtained by taking a snapshot of substantially all or of only a part of the peach half. But, in order to obtain accurate separation or classification or grading of peach halves, preferably incremental areas of the peach half are viewed in succession in a scanning action so that small local regions on a peach half have a proportionately greater effect on operation of the apparatus.

Further, from an inspection of FIGURE 4, it is noted that the particular shape of the aperture of tube 41 results in a sharp and quick transition from the condition wherein no peach area is being observed to a condition wherein the full viewing area is observed; this being true because of the particular curvature of the elliptical aperture in relationship to the shape of the projected peach half. Thus, the area A of the peach half which is being viewed in FIGURE 4 is substantially equal to the full area B and viewing of a substantial portion is accomplished in a minimum time as the peach half P travels in the direction indicated by the arrow E; likewise, as the peach half P leaves the field of vie-W, it is evident that the area C of the peach half which is viewed becomes increasingly smaller in a very short time to effect a sharp transition. Preferably, the aperture is of as small an area as possible. Satisfactory results have been obtained with peach half velocities of 30 inches per second with a spacing of approximately one and onequarter inches between adjacent edges of successive peach halves.

I have observed that in classifying comestibles, such as peach halves, spurious results may be encountered due to chlorophyll content of the comestible. When peaches are illuminated with light in the visible spectrum, it has been found that a large amount of infrared light is developed after the light is reflected from the peach and this is believed to be due to the chlorophyll. Since it is desired to classify the peach halves in accordance with color shades in the visible spectrum and since the presence of such infrared light influences some types of phototubes and therefore affects the accuracy of measurements, the effect of such infrared light is eliminated. For this purpose a very narrow band pass lter, which replaces lter 45 and which passes a band of light frequencies in the range of 660 to 680 millimicrons, may be interposed in front of the tube 20 when the same is a red-sensitive tube; then, to balance the system optically, a green filter, which replaces filter 44, is interposed in front of the tube 21 when the same is a green-sensitive tube. However, the addition of these two filters, when tubes 20 and 21 are redand green-sensitive, results in operation of the tubes with low light intensities, resulting in lowering the rate at which the peach halves may thus be inspected optically. In order to avoid lowering of such rate, preferably, as described above, the tubes 20, 21 are of the RCA-93 lA type and each has the characteristic color curve illustrated in FIGURE 8, and a red filter 45 is interposed in front of such tube 21 while a green filter 44 is interposed in front of the other identical tube 2i). The result in either case is that means are provided for preventing the infrared reflection developed by the chlorophyll from influencing the measurements.

The light thus impinging on the phototubes 20 and 2l determines the resistance of the same, Thus, when viewing a green peach, the resistance of the green tube 21 is relatively low and the resistance of the red tube 2@ is relatively high; conversely, when viewing a ripe peach, the resistance of the green tube 21 is relatively high and the resistance of the red tube 2i? is relatively low. These changes in the resistance of the green and the red tubes, occasioned by different color shades of a particular portion of a peach half being viewed, are used to eiect changes in conductance of an amplifier or electrometer tube 24 which is coupled to the green and red tubes in the manner now described.

Briefly, the photocells 20 and 21 are connected in a bridge circuit and are connected to produce a differential elect on the `control grid of the So-called electrometer tube 24. The amplified output current variations of tube 24 are applied to the control grid of discharge device 25 which is connected as a cathode follower. Depending upon the voltage drop in the cathode return circuit of tube 25, one or more of the thyratron type tubes 26, 27, 28, 29 is fired to thereby energize a corresponding one of the relays having the windings 30, 31, 32` and 33, respectively. For this purpose, the photocells Ztl, 21 are coupled to the control grids of each of the thyratron tubes 26, 27, 28, 29 to control their tiring. The function of these relays generally is to initiate the firing of a corresponding one of the thyratron tubes 34, 35, 36 and 37. The anode circuits of the tubes 34, 35, 36 and 37 include, respectively, the coils 50, 51, 52 and S3. These coils form an important part of a time delay or memory apparatus of the character shown and claimed in my copending patent application Serial No. 233,232, tiled June 23, 1951, now Patent No. 2,773,596, and assigned to the same assignee as the present application.

Preferably, the apparatus incorporates two rotating magnetizable discs 54 and '55 of paramagnetic material riven synchronously with movement of the endless peach conveying belt 10. For that purpose, the belt pulley shaft 56 is mechanically coupled to the disc shaft 57 by mechanical connections, indicated by the dotted line 58 in FIGURE l. The coils 52, 53, when energized, are energized only for a brief period of time and produce a magnetized spot on the corresponding discs 54 and 55. These magnetized spots, when mo'ved adjacent corresponding pickup `coils SllA, 51A, 52A and 53A, induce a corresponding voltage in the grid circuit associated, respectively, with tubes 50B, 51B, l52B and 53B, to lire the corresponding tube and produce a resulting energization of windings 13A, 14A, 15A, and 16A, respectively, for the aforementioned purpose o'f actuating the mechanisms 13, 14, 15 and 16, respectively, to remove the peach half into the corresponding receptacle 12A, 12B, 12C or 12D, as the case may be.

The particular form of ejecting mechanism 13, 14, 15 and 16, per se, forms no part of the present invention and may comprise either solenoid actuated kickers which actually engage the peach half, as shown in my aforementioned copending application Serial No. 80,865, now abandoned, or may comprise la plurality of air jets as set forth in my patent application Serial No. 232,975, filed June 22, 1951, and now Patent No. 2,713,409, assigned to the same assignee as the present application. These mechanisms 13, 14, 15 and 16, are actuated in accordance `with energization of the corresponding coils 13A, 14A, 15A, and 16A, and the connecting mechanisms between the coils and ejecting mechanism are indicated in schematic form 1by the dotted lines 13B, 14E, 15B and 16B.

A detailed description of the circuitry immediately associated with the photo'tubes 29 and 21 in FIGURES l and 2 now follows.

Before the specific circuitry associated with the phototubes Ztl and 21 is described, an inspection of the simpliiied circuit in FGURE 2 is referred to in the following brief description of operation.

It is observed that the phototubes 20 and 21 are serially connected across spaced terminals on the voltage dividing resistance 62 so that the current is allowed to ilow through such serially connected photo'tubes in the following path; from the tap 51 of positive potential through the lead 49 to the anode of tube 20, to the cathode of tube 20, to the anode of tube '21, to the cathode of tube 21 and to the negative terminal of such voltage dividing resistor 62. lt is noted that the phototubes 20 and 21 themselves act as voltage dividers, the division of voltage across the same being determined by the relative resistances of the phototubes 2@ and 21. Thus, when the light impinging on the phototubes 20 and 21 is predominantly red, the phototube 20 has -a relatively low resistance and the phototube 21 has a relatively high resistance, with the result that a relatively high voltage is developed across the phototube 21; conversely, when the light impinging on the tubes 2@ and 21 is predominantly green or blue a relatively small voltage is developed across the tube 21.

It is further noted that, when a peach half is not being viewed, a light predominantly red in color, produced by the constantly energized lamp 48, impinges on the phototubes 20 and 21. For this purpose, the light produced by the so-called biasing lamp 48 passes through the red filter S9, condensing lens 42 and half-silvered prism 43 onto the phototubes 2@ and 21 with equal intensity. Thus, normally, because of the biasing lamp 48, a relatively high voltage is developed across the green photo'tube 21 to cause the electrometer tube 24 to conduct heavily. This is so since the control grid of the tube 24 is thus maintained at a relatively high positive potential with respect to its cathode. As a result of such heavy current flow through electrometer tube 24, the potential of the anode of such tube 2li is depressed because of the relatively high voltage drop across the anode resistance 65. The voltage on the anode of tube 24 is applied through conductor 78 to the control grid of tube 25 so that, under this condition (when no peach half is being viewed) a relatively high negative voltage appears on the control grid of tube 25 to' bias the same beyond cutoff; and, as a result, there is substantially no current ilow through the cathode resistance 75. From the foregoing description, it is clear that the greener the peach half being viewed, the less will be the positive voltage developed on the control grid of the electrometer tube and, as a result, the greater the voltage drop across cathode resistor 75 becomes. The voltage thus developed across the resistor 7S serves as a measure o'f the degree of ripeness of the peach half, the riper the peach half the smaller is such voltage across resistor 75; and, conversely, the greener the peach half the greater the voltage across resistor 75.

It is, therefore, understood that the term measurement of the degree of ripeness of a peach half has reference to the magnitude of voltage developed across the resistance 75. This voltage developed on resistor 75 is applied, `on the one hand to the control grid of a so-called monitor tube 77 which, in general, serves to' condition other apparatus for sequential operation in the manner described later, and on the other hand such voltage on resistor 75 is applied to a so-called color adjustment cir-V cuit which involves the four potentiometer resistances 80, 81, S6 and `87, whereby selected levels of such voltage may be applied to the control grids of four corresponding tubes to cause a selected one of such tubes to fire, at predetermined threshold values, to effect a gradation in color sorting.

In general, the greenest peach half in a scale of ripeness causes the tubes 29 and 37 to be fired in sequence as controlled by the thyratron tube 77; a riper peach half causes the tubes 23 and 36 to be fired in sequence as controlled by the monitor tube 77; a still riper peach half causes the tubes 27 and 35 to be` fired in sequence as oontrolled by the monitor tube 77; a still riper peach half causes the tubes 26 and 3ftto be fired in sequence as controlled by the monitor tube 77; `and a select ripe peach half develops a voltage across the cathode resistor 75 which is insufficient in magnitude to re any of the tubes, whereupon the peach half instead of being ejected by either one of the mechanisms-13, 14, 15 or 16, is allowed to travel past the ejecting mechanism and be deposited in the receptacle 12.

A detailed description of the circuitry shown in FIG- URE l now follows.

The anode of phototube 21 is connected to the cathode of phototube 20, and their junction point is connected to the control grid of tube 24 and to one terminal of the grid resistance 60. The cathode of tube 24 is connected to the tap 61 on the voltage dividing resistance 62, and the other terminal of resistance 60 is connected through the movable tap on potentiometer resistance 64 to the negative terminal of resistance 62. One outside terminal of resistance 64 is grounded, while the other outside terminal of resistance 64 is connected to the cathode of tube 21. The cathode of tube 24 is bypassed to ground by means of condenser 65, and a similar condenser 66 serves to bypass one terminal of resistance 60 to ground.

Voltage is supplied to the voltage dividing resistance 62 by means of a conventional full-wave rectifier having the general reference numeral 67 which is considered to lbe a source of direct current. The anode of tube 24 is connected to the control grid of the cathode follower tube 25 and is also connected through resistance 68 to the tap 69 on resistance 62 `for the ow of spiace current through tube 24. The screen grid of tube 24 is returned to ground through resistance 70.

The anode and screen grid of tube 25 are both co-nnected to the adjustable tap 71 on resistance 62 and to one terminal of the voltage regulator tube 73, which has its other terminal grounded. In such case, a substantially constant voltage is maintained on the anode of tube 25. Phototube 20 has its anode grounded and the cathode of phototube 21 is connected to the negative terminal of resistance 62, such terminal being likewise connected to one terminal of the voltage regulator tube 74, which has its other terminal grounded.

Tube 25 has its cathode returned to ground through the output load resistance 75, and voltages developed across such resistance 75 are transferred, on the one hand, through resistance 76 to the control grid of the thyratron tube 77 and, on the other hand, through lead 78 to the so-called color adjustment circuit 79. Specifically, lead 78 is connected to one terminal of the parallel potentiometer resistances 80 and 81. The adjustable tap 80A on resistance S is connected through resistance 84 to the control grid of the thyratron tube 26, and the adjustable tap 81A on resistance 81 is connected through resistance 85 to the control grid of thyratron tube 27. The parallel connected resistances 80, 81 are serially connected with the second pair of parallel connected resistances 86, 87 and with the resistance 8S to ground. in other words, it is clear that the voltage drop across the cathode output resistance 75 is applied to a series circuit which includes rst the parallel connected resistances 80, 81, second the parallel connected resistances 86, 87, and third the resistance 88.

Fractional parts of such voltage-appearing on the taps 80A, 81A, 86A and 87A may then be applied, respectively, to the control grids of tubes 26, 27, 28 and 29. It is noted that the tap 86A is connected through resistance 90 to the control grid of thyratron tube 28, and that the tap 87A is connected through resistance 91 to the control grid of thyratron tube 29. It is thus clear that the pair of phototubes 20, 21 are coupled to the control grid of thyratron tube 26 for controlling the firing of thyratron tube .26; and such phototubes 20, 21 are coupled also to the control grid of corresponding thyratron tubes 27, 28 and 29 to control the tiring of such tubes. Tube 26 has its screen grid connected through resistance 92 to the tap 96 on voltage dividing resistance 62, and the screen grids of tubes 27, 28 and 29 are connected, respectively, through resistances 93, 94 and 95 to the tap 97 on resistance 62.

The anodes of tubes 26, 27, 28 and 29 are connected, respectively, to one terminal of relay windings 30, 31,

32 and 33. These relay windings control the operation of single pole double throw switches which, in normal relatively de-energized position, are as shown in FIGURE l, wherein the movable arms of such relays interconnect the bottom relay contacts in a series circuit. The movable arms of the relay switches are connected to one terminal of the corresponding relay windings 30, 31, 32 and 33.

The movable switch arm associated with the winding 33 is connected to a source of positive potential derived in the half-wave rectier circuit 100, which includes the tube 102. It is observed that the center tap of the high voltage secondary winding 104 is grounded, and that the cathode of rectifier tube 102 is connected to one terminal of the potentiometer resistance 105, which has its other terminal returned to ground through the voltage regulating tube 106. The junction point of resistance 105 and tube 166 is connected to one terminal of coil 33 by means of lead 107. Such lead 107 is of positive potential and is connected through the normally closed contacts of relay switch 33A to the relay coil 32, and likewise through the normally closed contacts of relay switch 32A to the relay winding 31, and likewise through the normally closed contacts of relay switch 31A to the relay winding 30. Thus, normally each of the relay windings 30, 31, 32 and 33 is connected to the positive lead 107, thus conditioning the corresponding `tubes 26, 27, 28 and 29 for tiring when a voltage of suitable intensity is applied to their corresponding control grids.

It is observed that the relay switches 30A, 31A, 32A and 33A serve also to control the firing of corresponding thyratron tubes 34, 35, 36 and 37 by applying voltage to their corresponding grids. The cathodes of each of the tubes 34, 35, 36 and 37 are grounded. The anodes of tubes 34, 35, 36 and 37 are connected, respectively, through magnetizing coils 50, '51, 52 and 53 to the lead 108 of positive potential, such lead 108 being connected to one terminal of the condenser 109 and to the adjustable tap on resistance 105, the other terminal of condenser 109 being connected to the negative terminal of voltage regulator tube 106. The screen grids of tubes 34, 35, 36 and 37 are each connected through a corresponding voltage dropping resistance and through lead 113 through the common decoupling and voltage dropping resistance 110 to a tap 47 on the voltage dividing resistance 62. The control grids of tubes 34, 35, 36 and 37 are each connected through corresponding grid resistances t0 the lead 111, which in turn is connected to the adjustable tap 112 on the voltage dividing resistance 62. Also, the control grid of tube 34 is connected through resistance 34A to the upper terminal of switch 30A; the control grid of tube 35 is connected through resistance 35A to the upper terminal of relay switch 31A; the control grid of tube 36 is connected through resistance 36A to the upper terminal of relay switch 32A; and the control grid of tube 37 is connected through resistance 37A to the upper terminal of relay switch 33A.

The control thyratron tube 77 has its cathode grounded, its screen grid connected through resistance 77A to the tap 96, and its anode connected through the control relay winding 77B to one terminal of the secondary winding 104, so that the anode of tube 77 is supplied with alternati-ng voltage. Rel-ay winding 77B controls the operation of the normally closed relay switch 77C, which normally grounds the screen grid lead 113 through resistance 114.

The operation of the circuit described above in detail is generally as follows. The thyratron tubes 26, 27, 23 yand 29 are normally in condition for tiring, since direct current is applied to their anodes through switches 30A, 31A, 32A, 33A, respectively. Thus, when any one of these tubes res it will continue to conduct until its corresponding anode voltage is reduced to 11 volts or lower. The control thyratron 77 has alternating voltage applied to its anode, and hence conducts only when the voltage 11 applied to its grid exceeds a predetermined positive threshold value. The thyratrons used are of the shield or screen grid type. By making the shield or screen grid more negative, a higher positive potential is required on the corresponding control grid to tire the tube.

As explained previously, when a green peach half P is being Viewed with light from light source 4%, the bias on tube 25 is reduced, causing it to conduct, it being noted that normally in the absence of a pe-ach `half the tube 25 is Ibiased in a nonconducting condition due to the biasing lamp. This causes `a positive voltage with respect to ground to be developed on the cathode of tube 25. Since the control grid of tube 77 is connected to the cathode of tube 25, the tube 77 lires when a relatively small positive voltage appears on its control grid (assuming that the positive half of the alternating current voltage wave is present on the anode of tube 77). When tube 77 fires, relay Winding 77B is energized, thereby disconnecting `one terminal of resistance 114 from ground and imposing a relatively high negative potential on the screen or shield grids of tubes 34, 35, 36 and 37 through resistance 110, thereby placing such tubes 34, 35, 36 and 37 in a noniiring condition. The control grids of tubes 26, 27, 28 and 29 are biased differently so that they lire at different values of voltage appearing on the cathode load resistance 75. When the voltage on the cathode of tube 25 is progressively raised, the tube 77 is lirst conditioned to lire, then the tubes 26, 27, 23 `and 29 in succession, and in that order, Iare conditioned for iiring. It is -observed that when tubes 26, 27, 28 and 29 are iired, the corresponding relay windings 30, 31, 32 and 33 are energized, thereby disconnecting the voltage supply to others. Thus, when the voltage on the cathode of tube 25 is sufficient to condition tube 2S for tiring, the anode voltage supplied to tubes 26 and 27 is disconnected and only tube 28 under such condition is fired, it being assumed that the voltage on the cathode of tube 25 is insutlicient at this time to cause tube 29 to fire.

It is observed that the tubes 34, 35, 36, 37 have a very high negative bias on their shield grids, and a heavy negative bias on their control grids when the tube 77 is being tired, i.e., when relay winding 77B is energized. Thus, when tubes 77 and 26 tire, the tube 34 does not conduct7 even though there is a positive voltage applied to the grid of tube 34 through the normally open contact of relay switch 30A. However, as soon as the peach half leaves the scanning head, the biasing lamp 4S causes the tube 24 and hence tube 25 to become nonconducting and the volta-ge in the cathode of tube 25 becomes zero, and the control tube 77 is cut oi. This allows relay winding 77B to become de-energized and allows closure of switch 77C. This causes the voltage on the screen grid of tube 34 to increase, so that the tube may be tired in response to the positive voltage applied to its control grid through resistance 34A. lt should be noted that at this stage the tube 77 is rendered nonconductive because of the alternating voltage applied to the anode of tube 77, while tube 26 remains conducting since a continuous potential is being applied to its anode and, of course, at this stage tube 34 is conditioned for tiring.

lt should be carefully noted that the precharged condenser 1129 is used to lire the tube 34, and once the tube 34 is thus tired, the condenser 1139 discharges to decrease the potential on lead 108 a suicient amount to prevent tiring. After condenser 109 is thus discharged in accordance with tiring of tube 34, the voltage on lead 107 is reduced suiciently to cause tube 26 to cease tiring7 especially since at this time, when the peach half has left the scanning head, the voltage on the control grid of tube 26 is relatively highly negative in nature. Then, as soon as tube 26 ceases to conduct, i.e., ceases tiring, its associated relay winding 3b is cle-energized, thus in turn allowing the bias on tube 34 to become highly negative.

From the foregoing description of the operation, it is evident that short pulses of energy are supplied to the magnetizing coils 50, 51, 52 and 53, depending upon the relative magnitude of the voltage developed on the cathode of tube 25, i.e., in accordance with the degree of ripeness of peach half P. Such short pulses of energy are used to produce magnetized spots on hardened steel discs 54, 55 running in synchronism with the endless belt 1t) upon which the peach halves are transported. Assuming as before that the pulse of energy is delivered to the coil 59, a magnetized spot appears on the disc 54. Then, when the disc travels in its orbital path adjacent the corresponding pickup coil 50A of relatively largenumber of turns, a corresponding voltage is induced in the coil 59A, and such voltage is applied to the control grid of the thyratron tube 53B to re the same. Similarly, the coil 511A is connected to the control grid of tube 52B, the pickup coil 52A is connected to the control grid of tube 51B, and the pickup coil 53A is connected to the control grid of tube Sil/B. The control grids of these tubes are normally biased negatively by small direct current voltage sources, and the anode of each is supplied with alternating current from the alternating current source 120, which has one of its terminals connected to the cathodes of tubes 50B, 51B, 52B and 53B and the other one of its terminals connected to the corresponding anodes through solenoid or relay windings 13A, 14A, 15A, 16A. Energization of any one of these windings 13A, 14A, 15A, 16A results in operation of the correspending peach half ejecting mechanism 13, 14, 15, 16, which mechanism operates to deflect or move the peach halves laterally from the belt 10 into corresponding receptacles 12A, 12B, 12C and 12D, all in accordance with the degree of ripeness of the peach halves. After the magnetized spot on the discs 5'4 and 55 have produced the above results, they are erased by conventional means which may comprise permanent magnets past which such magnetized spots travel for purposes of demagnetizing or erasing the same, as described in my copending application Serial No. 233,232.

Description of voltage regulating circuit for lamps 40 In general, the purpose of the apparatus now described is to produce a constant regulated voltage between the conductors 211, 212 to which opposite terminals of incandescent lamps 40 are connected.

Generally, as is described in detail hereinafter, the voltage across light sources 40, supplied with current from the secondary transformer winding 250 is regulated by automatically increasing or decreasing, as the case may be, the ow of an auxiliary current component through series regulating resistance 219, to thereby control the voltage drop across resistance 219. Such auxiliary current component flows to the primary winding 249 which energizes an energy absorbing circuit which includes the variable resistances 242, 243 as components thereof.

The arrangement includes two photoelectric cells or phototubes 214, 215, each being sensitive to different spectral distributions of light emitted from the incandescent light source 216. Thus, the phototube 214 is predominantly more sensitive to the green light emitted by the source 216, whereas the other phototube 215 is predominantly more sensitive to the red light emitted by the source 216.

The light source 216 has its opposite terminals connected to the secondary winding 250 through the adjustable resistance 217 and voltage dropping resistance 218. The character or spectral distribution of the light emitted from the source 216 is dependent on the magnitude of the voltage applied thereto. This is a common wellknown characteristic of a conventional incandescent lamp. For example, when the applied voltage is low, the light emitted is predominantly more red than when the voltage applied is high. Conversely, when the voltage applied to the light source 216 is relatively high, its lament iS heated to a greater extent to cause the emission of a light that is more green than when the applied voltage is low.

It is observed that the phototubes 214, 215 are serially connected with the outside terminals of the voltage source 230 so that a current is allowed to tiow through such circuit. Essentially the phototubes 214, 215 act as a voltage dividing network, the voltage being divided in accordance with the relative magnitudes of the resistances of the phototubes 214, 215. It is noted that the green phototube 214 is included in the grid circuit of the electrometer tube 227 to automatically vary the grid voltage of the tube 227. It is understood that, when the voltage on the lamp 216 is relatively high, predominantly more green light is emitted fromV the source with the result that the resistance of the green tube 214 is decreased whereas the resistance of the red tube 215 is increased; but, since the current ow is the same through the two tubes 214, 215 (assuming no grid current in tube 227), the voltage across the green tube 214 is decreased to thereby render the control grid of tube 227 less positive; i.e., the amount of current owing through the electrometer tube 227 is decreased under this condition.

Thus, assuming that the voltage between conductors 211, 212 tends to decrease to thereby decrease the intensity of the emitted light and to increase the redness of the light, the resistances of both the red-sensitive cell 215 and the green-sensitive cell 214 increases as a result in diminution in intensity of the light; however, the resistance of the green-sensitive cell increases a greater proportionate amount than the increase in resistance of the redsensitive cell due to the increased redness of the emitted light, thus providing a differential control effect. This differential control effect is in accordance with the difference between the changes in the resistance in the redand green-sensitive cells stimulated by the light falling thereon. Conversely, assuming that the voltage between the conductors 211, 212 tends to increase, the resistance of the green-sensitive tube decreases, as indicated previously, to a greater extent than the simultaneous decrease in resistance of the red-sensitive tube. These tubes 214, 215 may inherently have the aforementioned characteristics or they may be identical tubes with a green filter 220 in front of the phototube 214 and a red filter 221 in front of the phototube 215. Also, an iris diaphragm 222 may be used to control the amount of light falling onto the tube 215. Preferably, these tubes are each inherently more sensitive to different spectral distributions of light energy and the associated green and red filters 220, 221, respectively, are used to impart a greater sensitivity to the arrangement. For example, the phototube 215 may be a type 919 phototube, whereas the green-sensitive phototube 214 may be a type 935 phototube. The phototubes 214, 215 may be considered to be connected in an essentially balanced bridge circuit which includes in a first arm thereof the phototube 215, in the second arm thereof the phototube 214, in the third arm thereof the battery included between the lead 223 and the variable tap 224, and in the fourth arm thereof the battery included between the variable tape 224 and the lead 225. This substantially balanced Vbridge circuit includes a galvanometer arm which comprises the grid cathode of the electrometer tube 217. Specifically, the phototubes 214, 215 are serially connected with the source 230; i.e., the cathode of tube 215 is connected directly to the anode of the phototube 214 and their junctionpoint is connected to the control grid of tube 227. The cathode of the electrometer tube 227 is connected to the variable tap 224 on the voltage source comprising the battery 2301, which has its negative terminal connected to the cathode of the phototube 214 and its positive terminal connected to the anode of phototube 215, such positive terminal being grounded.

Preferably, this circuit thus far described is initially adjusted by first suitably positioning the variable tap 224 and then controlling the amount of light impinging on the phototube 215 by Varying the opening in the variable iris diaphragm 222. It is observed that the same current ows through the phototubes 214, 215 since they are serially connected (assuming no grid current in tube 227) but, as mentioned above, the resistances of the tubes 214, 215 change in accordance with spectral distributions of light energy emitted from the light source 216, to thereby, in turn, produce corresponding voltage variations in the galvanometer arm of the bridge including the grid and cathode of tube 227. These voltage variations applied between the grid and cathode are amplified in tube 227 and appear in amplified form on the anode 231. The anode 231 and its associated screen grid are connected through the potentiometer type load resistance 233 to the positive terminal of source 230. The amplified voltages appearing on the anode 231 may be applied to different utilization networks, and the one described in particularity hereinafter is merely exemplary of others used to accomplish the same purpose.

Specifically, the amplified voltage appearing on the load resistance 233 is applied to the control grids of tubes 236, 237. The cathodes of tubes 236, 237 are grounded and the control grids of these tubes are connected respectively through resistances 238 and 239 to the negative terminal of the bias battery 243, which has its positive terminal connected to an adjustable tap on resistance 233. Thus, a portion of the voltage appearing across the serially connected load resistance 233 and battery 243 is applied to the control grids of tubes 236, 237. The anodes of these tubes, as well as their associated screen electrodes, are connected through variable resistances 242, 243 to the outside terminals of the secondary center tapped winding 245 of the transformer 246, the center tap on the Winding 245 being connected to the grounded `cathodes of tubes 236 and 237 through the ammeter 234. The primary winding 249 of transformer 246 has its opposite terminals connected to the conductors 210 and 211.

The tubes 236 and 237 serve essentially as rectifier tubes and are productive of different amounts of current flow in the resistances 242, 243, depending upon the intensity of the voltage applied to the control grids of such tubes. Thus, assuming tubes 236, 237 draw relatively large current in the primary winding 249, in response to a relatively high voltage applied to the control grids of tubes 236, 237, the current thus supplied to the primary winding 249 passes through the series regulating resistance 219, to, in turn, cause a diminution in voltage between the conductors 210 and 211.

It is noted that the lower terminal of winding 249 is connected through lead 211 to one terminal of the secondary winding 250, while the upper terminal of primary winding 249 is connected through lead 212 and the series regulating resistances to the other terminal of the winding 250. The transformer 251 has the primary winding 253 connected to alternating voltage source 253A. A pilot light 254 maybe connected across the terminals of the secondary winding 251).

Thus, in operation, assuming that the voltage across secondary winding 250 is increased, the tendency then is for the voltage across the light source 40 to likewise increase, but this tendency is counteractcd by an increased current flow through the voltage dropping resistance 219, as demonstrated later. In response to this assumed increase in voltage across secondary winding 250, the filament of light source 216 is heated additionally to cause the amount of green light emitted thereby to increase in proportion to the red light to thereby proportionately decrease the resistance of green tube 214 and proportionately increase the resistance of red tube 215 with the result that there is a decrease in the voltage drop across the green tube 214. Accordingly, the control grid of tube 227 becomes more negative with respect to its cathode and the voltage drop across the load resistance 233 is decreased with the result that the control grids of tubes 236, 237 become more positive, thereby causing a greater 15 current flowth-rough thc-:primary winding 249 and resistance 219. This resulting increase in voltage drop across resistance 219 thus produces a compensatory effect for the increase in voltage across the winding 250. Thus, the voltage across the lamp 40 is maintained substantially constant within very close tolerance.

Preferably, for increased life and decreased aging, the lamp 216 is energized with voltage smaller than its rated voltage. Consequently, the light emitted from the lamp 216 is normally predominantly on the red side, hence the use of the diaphragm 222 in front of the red phototube 215. For example, the secondary winding 250 may deliver a voltage of 6.3 volts, and the lamps 40 having a normal rating of 6.3 volts are operated at volts because of the voltage drop across resistance 219; likewise, the voltage on lamp 216 is dropped to approximately 5 volts by the series resistances 217 and 21S.

It is noted that the green tube 214 forms a return or so-called grid leak for the control grid of tube 227, a conventional resistance being omitted for purposes of increased sensitivity.

The adjustment of resistances 242 and 243 is somewhat critical since, if the resistances 242, 243 are too low, the voltage across the lamps 40 is overcorrected. However, once adjusted, the resistances 242, 243 need not be changed.

It has been observed that photoelectric emission from the tubes 214, 215 in response to changes in light intensity has proven to be substantially linear and substantially unaffected by temperature changes occurring in wide range. Preferably, the filament voltage applied to the electrometer tube 227 is below its rated voltage, for purposes of stability and increased life. The voltages on the photoelectrie cells 214, 215 are maintained at approximately 221/2 volts, well above that necessary to collect all electrons emitted from their corresponding cathodes and well below the maximum of 20G` volts prescribed for these tubes.

Description of modiyed arrangement shown in FIGURE 9 The arrangement shown in FIGURE 9 provides a measurement of the color of an article in accordance with a so-called snapshot of the article, it being understood that this arrangement is not necessarily limited to color determinations of peaches and is likewise not necessarily limited to articles which have essentially a circular cross section as, for example, peaches and pears, but the arrangement is applicable to other comestibles such as, for example, asparagus, and is applicable also to obtaining measurements from articles which are not necessarily comestibles.

Referring to FIGURE 9, an auxiliary light source 307 and an auxiliary photocell 300 are provided so as to render the apparatus which is described hereinafter effective to make a color determination or measurement immediately after the leading edge of the article, shown in FIGURE 9 as a peach half P, is interpositioned in the light path between the light source 307 and photocell 300. The photocell 300 has its anode connected to the positive terminal of voltage source 302 through the so-called load resistance 301, the cathode of the photocell 300 being connected to the negative terminal of source 302 so that a relatively large voltage drop normally appears across the resistance 301 when there is no peach half P blocking the iiow of light to the photocell 300.

This voltage drop across resistance 301 is used to normally bias the thyratron tube 304 so that it is normally nonconducting. For this purpose, the nega-tive terminal of `resistance 301 is connected to the control grid of tube 304 while the positive terminal of resistance 301 is connected to the positive terminal of source 305 which has its negative terminal connected to the cathode of tube 304. The voltage appearing across resistance 301 is greater than 4the voltage of source 305 so that, as mentioned previously, the tube 304 is normally nonconducting. The cathode of tube 304 is returned to ground through the potentiometer type resistance 307 having the taps 97A and 96A thereon. The anode of tube 304 is connected to the positive terminal of voltage source 310 through the condenser charging resistance 311, the `negative terminal of source 310 being grounded. A condenser 314 h-as one of its terminals connected to the anode of tube 304 and the other one of its terminals grounded so as to be charged by the source 310 through the relatively high resistance 311.

It is understood from the foregoing description that immediately when the leading edge of the peach half P cuts off the light which normally passes from the source 307 to the photocell 300, the control grid of tube 304 becomes sufliciently positive to cause the tube 304 to conduct. The space current for tube 304 is supplied essentially from the prechatrged condenser 314 which, however, is charged at a predetermined rate in accordance with the magnitude of resistance 311. Thus, when the tube 304 begins to conduct, condenser 314 is discharged at a relatively rapid rate, much faster than the charging rate of the condenser, so that the voltage on the anode of tube 304 is quickly depressed to a relatively small magnitude insuflicient to cause the tube 304 to conduct. The tube 304 is thus rendered nonconducting within a relatively short period of time even though a peach half P at that particular moment may be blocking the transmission of light from the source 307 to the photocell 300.

When the tube 304 conducts, as described above, for a brief period of time, a voltage is developed across the cathode resistance 307, such voltage being used, in the manner described hereinafter, as an enabling voltage to enable the tubes 26, 27 28 and 29 (connected to the rest of the circuitry as described above except as described below) to lire for a comparable short period of time.

It is noted from the above description with respect to FIGURE 1 that the screen grid of tube 26 is connected to the tap 96 which is maintained at approximately 4.3 volts; and the screen grids of tubes 27, 28 and 29 are connected to the tap 97 which is maintained at approximately -8 volts. In the arrangement shown in FIGURE 9, the screen grids of tubes 26, 27, 2S and 29 are normally maintained at a more negative potential since the cathode of tube 304 is connected to the tap 320 on the voltage dividing resistance, such tap being at approximately -30 volts and being connected to the cathode of tube 304 through the isolating resistance 321. By these means the tubes 26, 27, 28 and 29 are in condition to conduct only when the tube 224 conducts. It is remembered that only one of such tub 26, 27, 28 and 29 is allowed to conduct at any one particular time, as described above in connection with the arrangement shown in FIGURE l, i.e., in accordance with the magnitude of voltage developed across the cathode follower resistance 75.

The time constant of the circuit 311, 314 is such that the tube 304 is fired not more than once in accordance with one comestible, but such tube 304 is tired by each comestible. This condition places distinct limitations on the time constant of the circuit 311, 314 with respect to the speed of travel of the comestibles P and their relative spacings. In other words, the speed of the peach half P must be fast in relation to the time constant of the circuit 311, 314 to assure complete passage of the peach half between the source 307 and the photocell 300 before the condenser 314 has been recharged to a suiciently high potential to tire tube 304. Also, some time must elapse after such passage of the peach half to allow the condenser 314 to be suiiiciently charged whereby the tube 304 is in condition for firing immediately when the leading edge of the next succeeding peach half is interpositioned between the source 307 and the photocell 300.

Preferably, as mentioned above, the photocells 20 and 21 are 931-A type phototubes having an S4 surface.

aeaale 17 The sensitivity of one of the tubes 93l-Av with respect to the color of the light impinging thereon is represented in FIGURE 8. In FIGURE 8 the abscissa extends from 3000 Angstrom Units to 7000 Angstrom Units. The ordinates are measured in terms of percentage sensitivity and the 100% relative sensitivity point falls between 3000 and 7000 Angstrom Units. The photocell is insensitive to ultraviolet light less than 3000 Angstrom Units since the glass envelope of the tube is opaque to ultraviolet below 3000 Angstrom Units. The tube has relative sensitivity at approximately 7000 Angstrom Units which is in the deep red. It is thus observed that phototube 93 l-A is relatively insensitive to infrared light which occurs above 7000 Angstrom Units and which, as described previously, is reflected copiously by the chlorophyll of the comestible.

The 931-A tube is preferred not only because it has the characteristic illustrated in FIGURE 8 but also since it is a multiplier type of tube having a relatively small capacity and high sensitivity thereby allowing rapid inspection measurements of peach halves.

With respect to the intensity of light which is actually used, using the apparatus described above, the measurement indicates that the intensity of light at the region occupied by a peach half while being scanned is approximately 250 foot candles, although it is thought at the present time that' the intensity of illumination is not critical in that the intensity of illumination may be increased substantially without the characteristic colors of the light source masking out the true color of the article or comestible being observed.

Further, while the apparatus described is intended for use to determine color characteristics of wet peach halves, the same general results may be obtained as described above when the comestible or article is dry.

It is further contemplate that the comestibles are initially graded according to size with comestibles in one particular grade or size passing under one particular scanning head. In other words, it is contemplated that there will be a different scanning head for each size peach. For that purpose, the scanning head is adjustably mounted as shown in FIGURE to allow focusing of the optical system on small as well as large peach halves, although lack of exact focusing does not appear to be a serious problem.

Further, as mentioned above, while the spots 40A on the lamp bulbs are obtained using white or aluminum paint, it may be possible for the same result to be obtained using black paint. However, white or aluminum paint is preferred since both inside and outside layers of the white or aluminum paint serve as reflectors thereby minimizing the possibility of the production of so-called black areas, ie., a more uniform light intensity is obtained using the white or aluminum paint.

One important aspect of the present invention, as mentioned above, and which cannot be overemphasized, is the fact that both red and green phototubes 20, 21, see, view, or observe simultaneously the same spot on the peach half at the same angle. This fact is demonstrated. graphically in the drawings by the point 200 in the half silvered prism 43 at which point both photocells 20 and 21 are considered to be present simultaneously and occupying the same space having as a center such point 200. The point 200 is defined at the intersection of three lines, one of such lines being the line 201 which represents the central axis of the light beam passing upwardly through the viewing tube; a second of such lines 202 represents the central axis of the light beam which is reflected by the half silvered prism or mirror onto the phototube 20; and the third of such lines, line 203, represents the central axis of the light beam which is transmitted through the half silvered mirror or prism 43. As noted before, both tubes 20, 21 may be considered to be thus coexistent at the point 200, both viewing a single unitary spot at the same angle. In this respect it is 18 noted that since the upper surface of the peach half is concave, the angle at which both photocells simultaneously view the peach half, while traveling, constantly changes; but in spite of this yboth cells 20, 21 see the peach at the same angle.

FIGURE 2 is presented to show that the viewing angle changes when and as the peach half moves. Thus, when the peach half rst enters the field of View, it is viewed simultaneously by both cells 20, 21 at an angle represented by the relatively large angle A. Later it is viewed at a small angle B, and when the peach is in midposition, as represented -by the line 204, it is viewed at an angle considered to Ibe zero. Subsequently, when the peach half leaves the central viewing position, it is viewed at an angle which progressively becomes larger, as represented by the angles D and E. Since this viewing angle constantly changes, lboth photocells are effectively placed optically at the same position and. connected electrically to balance out the effect of such changing viewing angle in the manner described above.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modications as fall within the true spirit and scope of this invention.

I claim:

1. A method of grading comestibles as: to rpeness, the steps comprising: moving said comestibles, illuminating comestibles with illumination substantially uniform in intensity to progressively illuminate different spots on the moving comestibles with said illumination, comparing differentially, while viewing the moving comestible, the intensity or shades of two colors derived from said illumination and reflected from the same single unitary progressive spots on the comestibles to develop an ininite number of measurements of said intensity or shade, and sorting the comestibles according to one of such measurements.

2. The method set forth in claim l including the step of diffusing light, with the resulting diffused light comprising said illumination.

3. The method set forth in claim l including the step of producing a pre-determined measurement of such degree, when there is no viewing of a comestible, that sort ing is prevented.

4. The method set forth in claim l including the step of rendering said measurements uninuenced by infrared reflectance effects which are produced as a result of the chlorophyll in said comestibles. V

5. The method set forth in claim l including the step of diffusing light, with the resulting dilused light comprising said illumination, and said viewing including moving said comestibles past an aperture having a projected area smaller than the projected area of said comestibles, with said diffused light passing through said aperture to effect said measurements.

6. The method set forth in claim l including the step of diffusing light, with the resulting diffused light comprising said illumination, and said viewing including moving said comestibles past an aperture having a projected area smaller than the projected area of said comestibles, with said diffused light passing through said aperture to effect lsaid measurements, and including also the step of rendering said measurements uninuenced by infrared reflectance effects which are produced as a result of the illumination of comestibles containing chlorophyll.

7. In apparatus of the charactecr described, means arranged to illuminate moving objects, a plurality of photoelectric cell means, each sensitive to different co1- lors and arranged to receive light reilected from the same `unitary spot on such objects, light diifusing means disposed between, on the one hand said objects and, on the other hand said illuminating means, and a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and means including said photoelectric cell means for comparing differentially the responses of said photoelectric cell means to said light reflected onto said photoelectric cell means.

8. In apparatus of the character described, a voltage source subject to variations in the output voltage thereof, a light source, means including said light source and said voltage source for illuminating objects with diffused light, said voltage source being connected to said light source, compensating means 4associated with said voltage source and said light source to effectively erase said variations in the supply voltage otherwise produced in the source of illumination, a first photoelectric cell predominately responsive to a first color, a second photoelectric cell predominately sensitive to a second different color and means directing light, after reflection, from a single unitary spot on said object simultaneously to said first and second photoelectric cells, and differential comparison means including said first and second photoelectric cells for comparing differentially the responses of said first and second photoelectric cells to said light reflected onto the same.

9. In a device for selectively classifying comestibles, the combination of: a plurality of photoelectric cell means, each sensitive to different colors and arranged to receive light reflected from comestibles at a point of selection, light projecting and diffusing means adapted to project diffused light of substantially uniform intensity upon said comestibles, at one particular instant of time,

`at said point of selection, means for placing comestibles ceive light reflected only from said single unitary spot,

means for actuating said selecting apparatus in accordance with said amplified current variations, and means for maintaining the current output of said photoelectric cell means at a predetermined minimum when no comestibles are at said point of selection.

l0. In a device for selectively classifying objects, the combination of: diffused light means directed upon a selecting point for illuminating objects with diffused light, a plurality of photoelectric light sensitive cell means each sensitive to different colors and arranged to receive light reflected only from a single unitary spot on said objects at said selecting point, means for moving objects past said selecting point to thereby produce a scanning action, differential comparison means including said plurality of photoelectric cell means for producing a current iiow representative of a differential comparison of said colors, an electromagnetic device electrically related to said differential comparison means and controlled thereby, and means for maintaining the current output of said photoelectric cell at a predetermined magnitude when no object is at the selecting point, said output being outside of the range of values which are obtained when an object is at the selecting point.

l1. In an arrangement for selectively classifying comestibles as to degree of maturity, two serially connected photoelectric cells in a series circuit with the cathode of one of said cells connected to the anode of the other f said cells, each sensitive to different color shades of light refiected from the comestibles, a continuous unidirectional source of voltage, said photoelectric tubes being energized lfrom said continuous unidirectional source of voltage which is connected in said series circuit with the positive terminal of said source being connected to the anode of said one cell and with the cathode of said source being connected to the cathode of said other cell to produce a current flow through said photoelectric cells, means `for illuminating comestibles with diffused light, means applying light reflected from a single unitary spot, at one particular time, simultaneously to each of said cells, an amplifier having one o-f its input terminals connected to the anode of said other cell and the other one of its input terminals connected to an intermediate point on said voltage source, and electromagnetic means coupled to an output terminal of said amplifier and operated and controlled by voltage variations in the input circuit of said amplifier for effecting classification of different comestibles as to degree of maturity.

12. In a device :for selectively classifying comestibles according to degrees of maturity, two serially connected photoelectric cells comprising a serial circuit with the 'anode of one of said cells connected to the cathode of the other of said cells, each cell being sensitive to different colors reflected from comestibles, means connected in said serial circuit and producing a current flow through said photoelectric cells, means for illuminating comestibles with diffused light, means applying light reflected from a single unitary spot on said comestibles, at one particular time, simultaneously to each of said cells, and means controlled and operated in accordance with voltage variations in said serial circuit to automatically classify comestibles according to maturity or color shade.

13. The arrangement set forth in claim 7 in which said cell means comprises a pair of photocells, each of which views said objects at the same viewing angle.

14. The arrangement set forth in claim 8 in which said first and second cells are effectively placed at the same position to view an object at the same angle.

15. The arrangement set forth in claim ll in which means effectively position said cells in the same position wherein they both view the comestible at the same viewing angle.

16. A method of grading comestibles as to ripeness, the steps comprising: subjecting a comestible to substantially diffused illumination, viewing the comestible from effectively a single viewpoint, and comparing differentially the intensity or color shade of two colors reiiected from a single unitary spot on the comestible according to a scale of distribution of color shade.

17. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted along a path including a viewing zone providing visibility of the surface of each article during its passage through said viewing zone, means for illuminating the articles during passage through said viewing zone, photoelectric means arranged to view simultaneously the same portions of the surface of an article during movement through said viewing zone, said photoelectric means including a pair of differentially connected phototubes positioned to receive light reflected from said same portions of said article in said viewing Zone for effecting a differential comparison of color shades reflected from said same portions, and a thyratron having a control grid, said pair of phototubes being connected to said control grid and controlling the firing of the thyratron in accordance with said differential comparison of color, selecting means, and means responsive to firing of the thyratron by said phototubes for actuating said selecting means for effecting selection of said articles.

18. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted along a path providing Visibility of the surface of each article, means for illuminating the articles during passage through said viewing zone, photoelectric means arranged to view si- 21 n-ultaneous'ly the same portions ofthe surfaceofan article during movement along said path, said photoelectric means including a pair of differentially acting phototubes, a thyratron having its input circuit arranged to receive dierential electrical signals from said pair of phototubes and subject to firing by such signals, and masking means confining the region of view of an article by the phototubes to a region which is relatively narrow in the direction of movement of the article, and means coupled to the output circuit of said thyratron and responsive to said photoelectric means for effecting selec- Vtive acceptance or rejection of said articles.

19. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted through a viewing zone, means for alluminating the articles during passage through said viewing zone, photoelectric means for viewing the articles during passage through said viewing zone, said photoelectric means including a pair of phototubes viewing simultaneously substantially the same area of each article in said viewing zone, arranged to have different color responses and connected to provide a differential response, said photoelectric means also including a thyratron having a control grid, said pair of phototubes being connected to said control grid and' controlling the firing of lthe thyratron, and means responsive to firing of the thyratron fby said phototubes for actuating selecting means for effecting selection of said articles.

20. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted along a path including a viewing zone providing visibility of each article during its passage through said viewing zone, means for illuminating the articles during passage through said viewing zone, photoelectric means arranged to View simultaneously portions of the surface of an article during movement through said viewing zone, said photoelectric means including a pair of differentially connected phototubes, each sensitive to different intensities or color shades and positioned to receive light reflected from the same spot of an article in said viewing zone and a thyratron having a control grid, said pair of phototubes being connected to said control grid and controlling the firing of the thyratron, and means responsive to firing of the thyratron by said phototubes for actuating selecting means for effecting selection of said articles.

2l. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted along a path providing visibility of each article, means for illuminating the articles during passage through said viewing zone, photoelectric means arranged to view simultaneously portions of the surface of an article during movement along said path, said photoelectric means including a pair of differentially acting phototubes sensitive to different intensities or color shades, a thyratron arranged to receive differential electrical signals `from said pair of phototubes and subject to firing by such signals, and masking means confining the region of View of an article by each of the phototubes to the same region which is relatively narrow in the direction of movement of the article, and means responsive to said photoelectric means for effecting selective acceptance or rejection of said articles.

22. Photoelectric sorting apparatus including means for effecting movement of articles to be sorted through a viewing zone, means for illuminating the articles during passage through said Viewing zone, photoelectric means for viewing the articles during passage through said viewing zone, said photoelectric means including a pair of phototubes viewing simultaneously substantially the same area of each article in said viewing zone, arranged to have different color responses and connected to provide a differential response, said photoelectric means also including a thyratron having a control grid, said pair of phototubes being coupled to said control grid and controlling the firing of the thyratron, and means responsive to firing of the thyratron by said phototubes for actuating t selecting means for effecting selection of said articles.

23. In apparatus of the character described,- means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light rellected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the objects by said photoelectric cell means, means associated with said photoelectric cell means for comparing differentially, while scanning the object, the intensity or shade of two colors refiected from the objects, with the light reliected from the same single unitary fractional parts of the objects, to develop an infinite number of measurements of said intensity or shade, and means sorting the objects according: to one of such measurements.

24. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light refiected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the objects by said photoelectric cell means, means associated with said photoelectric cell means for comparing differentially, While scanning the object, the intensity or color shade of two colors reflected from the objects, with the light reflected from the same single unitary fractional parts of the objects to develop an infinite number of measurements of said intensity or color shade, means sorting the objects according to one of such measurements, and means for impressing a light of predetermined color outside the range of said color shades on said photoelectric cell means when no objects are at said point of selection.

25. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reected from said objects is the light diffused by the diffusing means, a scanning head `having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture havesagera aperture to produce a scanning of the objects by said photoelectric cell means, means associated with said photoelectric cell means for comparing differentially, while scanning the object, the intensity or color shade of two colors reflected from the objects with the light reflected from the same single unitary fractional parts of the objects to develop an infinite number of measure ments of said intensity or color shade, a thermionic tube circuit connected to said differentially comparing means and adapted to amplify current variations thereof, said cell means being sensitive only to the light reflected from said single unitary fractional parts, and electromagnetic means electrically related to said circuit and controlled in accordance with one of said measurements for directing objects which do not reflect light having a predetermined intensity or color shade.

26. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movements to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the objects by said photoelectric cell means, means associated with said photoelectric cell means ifor comparing differentially, While scanning the object, the intensity or color shade of two colors reflected from the objects with the light reflected from the same single unitary fractional parts of the objects to develop an infinite number of measurements of said intensity or color shade, a thermionic tube circuit connected to said differentially comparing means and adapted to amplify current variations thereof, said cell means being sensitive only to the light reflected from said single unitary fractional parts, electromagnetic means electrically related to said circuit and controlled in accordance with one of said measurements for directing objects which do not reflect light having a predetermined light intensity or color shade, and means for maintaining the current output of said photoelectric cell at a predetermined magnitude and for resetting said electromagnetic means when there are no objects at said point of selection.

27. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the same by said photoelectric means, means associated with said photoelectric cell means for comparing differentially, while scanning the object, the intensity or color shade of two colors reflected from the objects with the light reflected from the same single unitary fractional parts of the objects to develop an infinite number of measurements of said intensity or color shade, said photoelectric cell means being two serially connected photoelectric cells with the cathode of one of said cells connected at a junction point to the anode 0f the other of said cells, each cell being sensitive to different light intensity or color shades of light reflected from the objects, a unidirectional source of voltage, said photoelectric cells being energized from said unidirectional source of voltage, means applying light reflected from the same single unitary fractional part, at one particular time, simultaneously to each of said cells; and a thermionic amplifier responsive to said differentially comparing means and having one of its input terminals connected to said junction point of the serially connected cells andthe other one of its input terminals connected to an intermediate point on said voltage source, and electromagnetic means coupled to an output terminal of said amplifier and operated and controlled by voltage variations in the input circuit of said amplifier for effecting classification of different objects as to degree of maturity.

28. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having `a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the objects by said photoelectric cell means, said photoelectric cell means being associated with means for comparing differentially, while scanning the object, the intensity or color shade of two colors reflected from the objects with the light reflected from the same single unitary fractional parts of the objects to develop an infinite number of measurements of said intensity or color shade, means sorting the objects according to one of such measurements, said photoelectric cell means including two serially connected photoelectric cells comprising a serial circuit with the anode of one of said cells connected to the cathode 0f the other of said cells, each cell being sensitive to different light intensities or shades reflected from objects, and means applying said light reflected from a single unitary fractional part of said objects, at one particular time, simultaneously to each of said cells.

29. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to different light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes `from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dirnension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning ofthe objects by said photoelectric cell means, means associated with said photoelectric cell means for comparing differentially, while scanning the object, the intensity or color shade of two colors reilected from the objects with the light reected from the same single unitary fractional parts of the objects to develop an infinite number of measurements of said intensity or color shade, said photoelectric cell means being two serially connected photoelectric cells comprising a serial circuit with the anode of one of said cells connected to the cathode of the other of said cells, a continuous voltage source energizing said serial circuit, each one of said cells being sensitive to different colors reilected from the objects, means applying light reflected from a single unitary fractional part of said objects, at one particular time, simultaneously to each of said cells; a voltage amplifier responsive to said differentially comparing means and having one of its input terminals connected in said serial circuit and the other one of its input terminals connected to an intermediate point in said voltage source to produce current variations in the output circuit thereof, and selecting apparatus coupled to said output circuit and operated in accordance with one of said measurements.

30. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to diierent light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means disposed between, on the one hand, said objects and, on the other hand, said illuminating means so that the light reflected from said objects is the light diffused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an `object as it moves, means for moving said objects past said aperture to produce a scanning of the same by said photoelectric means, means associated with said photoelectric cell means for comparing differentially, while scanning the object, the intensity or color shade of two colors reflected from the objects, with the light reflected from the same single unitary fractional parts of the objects vto develop an infinite number of measurements of said intensity or color shade, said photoelectric cell means including two serially connected photoelectric cells comprising a serial circuit with the anode of one of said cells connected to the cathode of the other of said cells, each cell being sensitive to different colors reflected from said objects, and each cell being insensitive to infrared effects produced by the chlorophyll in said objects, and means coupled and responsive to said differentially comparing means for sorting the objects according to one of such measurements.

3l. In apparatus of the character described, means arranged to illuminate moving individual objects having a generally circular cross section, a plurality of photoelectric cell means, each sensitive to dierent light intensities or color shades and arranged to receive light reflected from the same spot on such objects, light diffusing means diposed between, on the yone hand, said Objects and, =on the other hand, said illuminating means so that lthe light reflected from said objects is the light diifused by the diffusing means, a scanning head having an aperture through which reflected light passes from said objects to said photoelectric cell means, said aperture having a projected area substantially less than the projected area of said objects, and having a dimension substantially equal to the dimension of the object as measured perpendicular to its direction of movement to thereby provide progressive scanning of fractional parts of an object as it moves, means for moving said objects past said aperture to produce a scanning of the same by said photoelectric cell means, means associated with said photoelectric cell means for comparing difierentially, while scanning the object, the intensity or color shade of two colors `reflected from the objects with the light reflected from the same single unitary fractional parts of the objects, to develop an infinite number of measurements of said intensity or color shade, and means coupled and responsive to said differentially comparing means or sorting the objects according to one of such measurements at a point remote from said point of selection, said last mentioned means incorporating time delay means allowing an object to Abe moved from said point of selection to said remote point before said object is sorted.

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